Bioavailability of a natural isomer mixture as compared with synthetic all-trans-beta-carotene in rats and chicks

J Nutr. 1989 Jul;119(7):1013-9. doi: 10.1093/jn/119.7.1013.


The unicellular halotolerant alga Dunaliella bardawil was previously shown to contain high concentrations of beta-carotene composed of about equal amounts of the all-trans and 9-cis isomers. One-d-old chicks and 7-wk-old male rats were fed diets supplemented with synthetic all-trans-beta-carotene or dry D. bardawil at equivalent levels of beta-carotene. The chicks were fed diets containing up to 0.025% beta-carotene for 2 mo, and the rats up to 0.1% beta-carotene for 2 wk. Liver analyses at the end of these periods indicated that both species showed at least a tenfold higher accumulation of the algal beta-carotene isomer mixture than of the synthetic all-trans-beta-carotene. The ratio of 9-cis-beta-carotene to the all-trans isomer in the livers of the algae-fed rats and chicks was similar to or higher, respectively, than that present in the algae. Retinol plus retinyl ester accumulated to a similar extent in the rats and chicks fed diets supplemented with synthetic all-trans or the natural isomer mixture of beta-carotene. The preferable accumulation of the natural isomer mixture of beta-carotene suggests that attention should be paid to the different sources of beta-carotene when testing their efficacy in effects other than providing retinol, such as in their possible role in the prevention of some types of cancer.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Administration, Oral
  • Animals
  • Carotenoids / administration & dosage*
  • Chickens
  • Chromatography, High Pressure Liquid
  • Eukaryota*
  • Intestinal Absorption
  • Liver / metabolism
  • Male
  • Nutritive Value
  • Rats
  • Stereoisomerism
  • Structure-Activity Relationship
  • beta Carotene


  • beta Carotene
  • Carotenoids